Restful sleeping is usually associated with comfort, and comfort is in turn associated with minimum body shifts during the course of a night. Recognized major causes of body shifts while sleeping, and hence, poor sleep, are the buildup of pressure on prominences of the body and poor postural support. Pressure on prominences of the body causes tissues of the body at those prominences to be put in compression so as to restrict capillary blood flow to those prominences. The pressure which causes a discontinuance of capillary blood flow is called ischemic pressure. Fifteen inches of water (28 mmHg) is normally considered to be the ischemic threshold. Those parts of the body which are subjected to pressures above the ischemic threshold cause discomfort, and hence, cause the person to shift the body to eliminate the distress and remove the excessive pressure from those prominences.
The lack of postural support from an improper mattress causes distortion of the spine. Distortion of the spine can occur within or beyond the normal physiological range of motion of the spine depending on the structural condition of the spine. As distortion occurs in the spine, ligaments are stretched and joint integrity is compromised. Nerve receptors within the ligaments and joints detect distortion and relay it to the brain where it is received on a conscious or subconscious level. Action is taken on a conscious or subconscious level to relieve the distortion by movement of the body. Spinal alignment can only be obtained when the natural curves of the body are maintained whether in the supine or side lying position.
There are in the prior art disclosures of air mattresses which attempt to maintain subischemic pressures over the full body and to provide uniform support of the body. Examples of such patents are U.S. Pat. Nos. 4,662,012; 4,005,236; and 3,605,145; and British Patent No. 1,545,806.
Torbet U.S. Pat. No. 4,662,012 represents one attempt to obtain subischemic pressure and spinal alignment of a person reclining atop a multiple zone air mattress. According to the disclosure of this patent, the zones are maintained at predetermined pressures at all times, both, when a person is resting atop the mattress and when the mattress is unoccupied. As a consequence, air must be bled off of the zones of the mattress when a person reclines atop the mattress in order to maintain the predetermined low pressures and additional air must be pumped into the zones when a person gets up off of the mattress in order to reinflate the zones to the predetermined pressure. Additionally, the pressure in the zones must be adjusted as the person reclining on the bed changes position on the mattress. This inflation and deflation of the zones of the mattress requires relatively expensive pumps and control equipment, the expense of which limits the application of the mattress.
It has therefore been an objective of this invention to provide a relatively inexpensive air bed which has many of the advantages of air beds disclosed in the above-identified Torbet patent.
Still another objective of this invention has been to provide a minimally expensive air bed having an inexpensive inflation control system for maintaining the bed at optimal pressures for achieving spinal alignment when a person is resting atop the mattress.
Still another objective of this invention has been to provide a relatively inexpensive air bed which may be customized or tailored for each person utilizing the bed for maximum comfort of that person and without the need for expensive controls to achieve that comfort level.